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From: Peter Pisciotta (no email)
Date: Mon Jul 03 2006 - 12:58:01 EDT
> Somewhere there must be a
> manufacturers rationale and test
> results that support the staged
> filter method and that it is not
> based on old stationary engine history
We already know a 2-micron filter will clog a lot
faster than a 10-micron filter - ask anyone on this
list who runs 2-micron primaries for validation -
chances are, they've had to change their primaries
while underway. Question is: is there benefit to
running 2/2 filtration (2-micron primary, 2-micron
secondary) over 10/2 (so-called stepped filtration,
the industry standard)?
I'll pose this question to the 2/2 folks: the fear is
having the eingine-mounted filter clog underway and
then have to replace, prime, and re-start the engine
(the "Oh my gawd" factor). But is there any
first-hand, real-life experience to back this up? I
mean, is there actually gunk that gets past a
10-micron primary and clogs a 2-micron secondary
between service intervals? Personally, I've never had
it happen, but concede it's possible so the question
becomes does that risk outweigh 1) vastly increased
liklihood of 2/2 clogging (monitoring is, after all, a
manual process and glass bowls eventually get foggy);
2) risk of possible engine damage due to elevated
vacuum and fuel temps; and finally 3) the remarkably
consistent guidance of billions of dollars of R&D and
warranty dollars?
But the 2/2 position seems so, well, logical - where's
the flaw? I suspect the answer lies in the microscopic
nature of the particles. We are worried about the
stuff we can see (fuel tank gunk - rust, dirt, water,
asphaltines, etc). The engine manufacturers are
worried about microscopic-sized particles. At that
level, they're okay with 10/2 filtration (in fact,
they recommend it). Sure, a 2-micron filter will
filter out the big crud, but unless the filter is very
large, it will load-up and clog, placing a burden on
the engine (their concern) and potentially cause the
engine to starve/die mid-ocean (my concern). According
to the experts (and my personal experience), using a
properly maintained 10/2 system will not cause the
2-micron secondary to clog and an unexpected engine
stop, but using a 2/2 system may.
So, I think I've laid out the 10/2 position pretty
well, albeit belabored (its not a simple position).
I'll look for the 2/2 folks to move past logic and
post their actual experiences with clogged 2-micron
secondaries when installed in a 10/2 system. Depending
upon that outcome (as I said, I've never had it
happen), I'll have to weigh that evidence with the
liklihood of having a 2-micron primary clog in a 2/2
system. I think that's the heart of the decision, at
least for me.
Peter
www.SeaSkills.com
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